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 Karl Franzens University Graz

Graz University of Technology 

Formation and Spectroscopy of Antihydrogen - Studying Fundamental Symmetries with Atomic Physics Techniques
Prof. Eberhard Widmann
Stefan Meyer Institute for Subatomic Physics Austrian Academy of Sciences
http://www.oeaw.ac.at/smi
17:15 - 18:15 Tuesday 11 May 2010 TUG P2

Antihydrogen, the simplest antimatter atom consisting of an antiproton and a proton, is an ideal system to study the fundamental CPT symmetry which postulates an exact symmetry between matter and antimatter. The advantage of antihydrogen comes from the fact that its CPT conjugate system, hydrogen, is known to extremely high precision: the 1S-2S two-photon transition to 10^-14 and the ground-state hyperfine splitting to 10^-12 relative.
Precision laser or microwave spectroscopy experiments require the formation of antihydrogen atoms at rest in the ground state. The ATHENA and ATRAP collaborations at the Antiproton Decelerator at CERN have succeeded in producing Antihydrogen from its charged constituents trapped in nested Penning traps. ATRAP and ALPHA, the successor of ATHENA, are currently trying to catch the formed antihydrogen in Ioffe-Pritchard type neutral atom traps for 1S-2S laser spectroscopy. We at ASACUSA are pursuing two different formation schemes, a "cusp trap" and a Paul trap, to generate an antihydrogen beam to measure the ground-state hyperfine structure in the same was as it was done for hydrogen in the 1940's. A new proposal AEgIS aims at the formation of an ultra-cold antihydrogen beam for a first ever measurement of the gravitational acceleration of antimatter. The status and outlook of experiments with antihydrogen will be reviewed.